Supplemental funds are requested to set up a radioimmunoassay for surface active material in primate lung. This method has been recently described by King and Clements; the principal investigator working with them has developed the antibody necessary for the assay in fetal monkey lung, tracheal and amniotic fluid. The assay will be used to measure the appearance and concentration of surface active lipoprotein in monkey fetuses of known gestational age. Prematurity and surface active lipoprotein deficiency is believed to be a cause of respiratory distress syndrome of infancy.